REGULATORY MATTERS (Regulatory Assets and Liabilities) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Regulatory Assets And Liabilities [Line Items]
Regulatory Assets—Current	$ 52,763		$ 51,619
Regulatory Assets—Noncurrent	150,584		191,077
Regulatory Liabilities - Current	(53,935)		(43,516)
Regulatory Liability, Noncurrent	(302,482)		(279,111)
UNS Energy
Regulatory Assets And Liabilities [Line Items]
Property Tax Deferrals Current	20,000	[1]	18,000	[1]
Derivative Instruments Regulatory Assets Current	1,000		11,000
Mine Fire Cost Deferral	10,000	[2]
PPFAC	14,000	[2]	15,000	[2]
DSM and LFCR Regulatory Assets Current	3,000	[2]
DSM			5,000	[2]
Other Current Regulatory Assets	5,000	[3]	3,000	[3]
Regulatory Assets—Current	53,000		52,000
Pension And Other Postretirement Benefits Noncurrent	80,000		139,000
Income Taxes Recoverable through Future Revenues	25,000	[4]	10,000	[4]
PPFAC—Final Mine Reclamation and Retiree Health Care Costs	25,000	[5]	22,000	[5]
Tucson to Nogales Transmission Line	5,000	[6]	5,000	[6]
Other Regulatory Assets Noncurrent	16,000	[3]	15,000	[3]
Regulatory Assets—Noncurrent	151,000		191,000
PGA	(15,000)		(17,000)
RES	(31,000)		(23,000)
Other Current Regulatory Liabilities Current	(8,000)		(4,000)
Regulatory Liabilities - Current	(54,000)		(44,000)
Net Cost of Removal for Interim Retirements	(292,000)	[7]	(267,000)	[7]
Income Taxes Payable through Future Rates	(6,000)		(6,000)
Deferred Investment Tax Credit	(4,000)	[8]	(5,000)	[8]
Other Regulatory Liabilities			1,000
Regulatory Liability, Noncurrent	(302,000)		(279,000)
Total Net Regulatory Assets (Liabilities)	(152,000)		(80,000)
TUCSON ELECTRIC POWER COMPANY
Regulatory Assets And Liabilities [Line Items]
Property Tax Deferrals Current	20,000	[1]	18,000	[1]
Derivative Instruments Regulatory Assets Current	1,000		2,000
Mine Fire Cost Deferral	10,000	[2]
PPFAC	4,000	[2]	7,000	[2]
DSM and LFCR Regulatory Assets Current	3,000	[2]
DSM			5,000	[2]
Other Current Regulatory Assets	5,000	[3]	2,000	[3]
Regulatory Assets—Current	42,555		34,345
Pension And Other Postretirement Benefits Noncurrent	75,000		130,000
Income Taxes Recoverable through Future Revenues	22,000	[4]	8,000	[4]
PPFAC—Final Mine Reclamation and Retiree Health Care Costs	25,000	[5]	22,000	[5]
Tucson to Nogales Transmission Line	5,000	[6]	5,000	[6]
Other Regulatory Assets Noncurrent	14,000	[3]	13,000	[3]
Regulatory Assets—Noncurrent	141,030		178,330
PGA	0		0
RES	(22,000)		(19,000)
Other Current Regulatory Liabilities Current	(2,000)		(2,000)
Regulatory Liabilities - Current	(23,701)		(20,822)
Net Cost of Removal for Interim Retirements	(254,000)	[7]	(231,000)	[7]
Income Taxes Payable through Future Rates	(5,000)		(5,000)
Deferred Investment Tax Credit	(4,000)	[8]	(5,000)	[8]
Other Regulatory Liabilities			0
Regulatory Liability, Noncurrent	(263,270)		(241,189)
Total Net Regulatory Assets (Liabilities)	(103,386)		(50,000)
UNS Electric
Regulatory Assets And Liabilities [Line Items]
Property Tax Deferrals Current	0	[1]	0	[1]
Derivative Instruments Regulatory Assets Current	0		6,000
Mine Fire Cost Deferral	0	[2]
PPFAC	10,000	[2]	8,000	[2]
DSM and LFCR Regulatory Assets Current	0	[2]
DSM			0	[2]
Other Current Regulatory Assets	0	[3]	0	[3]
Regulatory Assets—Current	10,000		14,000
Pension And Other Postretirement Benefits Noncurrent	3,000		5,000
Income Taxes Recoverable through Future Revenues	3,000	[4]	2,000	[4]
PPFAC—Final Mine Reclamation and Retiree Health Care Costs	0	[5]	0	[5]
Tucson to Nogales Transmission Line	0	[6]	0	[6]
Other Regulatory Assets Noncurrent	2,000	[3]	1,000	[3]
Regulatory Assets—Noncurrent	8,000		8,000
PGA	0		0
RES	(9,000)		(4,000)
Other Current Regulatory Liabilities Current	(6,000)		(1,000)
Regulatory Liabilities - Current	(15,000)		(5,000)
Net Cost of Removal for Interim Retirements	(12,000)	[7]	(11,000)	[7]
Income Taxes Payable through Future Rates	0		0
Deferred Investment Tax Credit	0	[8]	0	[8]
Other Regulatory Liabilities			1,000
Regulatory Liability, Noncurrent	(12,000)		(12,000)
Total Net Regulatory Assets (Liabilities)	(9,000)		5,000
UNS Gas
Regulatory Assets And Liabilities [Line Items]
Property Tax Deferrals Current	0	[1]	0	[1]
Derivative Instruments Regulatory Assets Current	0		3,000
Mine Fire Cost Deferral	0	[2]
PPFAC	0	[2]	0	[2]
DSM and LFCR Regulatory Assets Current	0	[2]
DSM			0	[2]
Other Current Regulatory Assets	0	[3]	1,000	[3]
Regulatory Assets—Current	0		4,000
Pension And Other Postretirement Benefits Noncurrent	2,000		4,000
Income Taxes Recoverable through Future Revenues	0	[4]	0	[4]
PPFAC—Final Mine Reclamation and Retiree Health Care Costs	0	[5]	0	[5]
Tucson to Nogales Transmission Line	0	[6]	0	[6]
Other Regulatory Assets Noncurrent	0	[3]	1,000	[3]
Regulatory Assets—Noncurrent	2,000		5,000
PGA	(15,000)		(17,000)
RES	0		0
Other Current Regulatory Liabilities Current	0		(1,000)
Regulatory Liabilities - Current	(15,000)		(18,000)
Net Cost of Removal for Interim Retirements	(26,000)	[7]	(25,000)	[7]
Income Taxes Payable through Future Rates	(1,000)		(1,000)
Deferred Investment Tax Credit	0	[8]	0	[8]
Other Regulatory Liabilities			0
Regulatory Liability, Noncurrent	(27,000)		(26,000)
Total Net Regulatory Assets (Liabilities)	$ (40,000)		$ (35,000)

[1] Property Tax is recovered over approximately a six-month period as costs are paid, rather than as costs are accrued.

[2] See Cost Recovery Mechanisms discussion above.

[3] TEP’s other regulatory assets include unamortized loss on reacquired debt (recovery through 2032), coal contract amendment (recovery through 2017), rate case costs (recovery over three years), environmental compliance costs, Springerville Unit 1 lease deferrals and other assets (recovery through 2014).

[4] Income Taxes Recoverable through Future Revenues are amortized over the life of the assets.

[5] Final Mine Reclamation and Retiree Health Care Costs stem from TEP’s jointly-owned facilities at the San Juan Generating Station, the Four Corners Generating Station, and the Navajo Generating Station. TEP is required to recognize the present value of its liability associated with final mine reclamation and retiree health care obligations over the life of the coal supply agreements. TEP recorded a regulatory asset because TEP is permitted to fully recover these costs through the PPFAC when the costs are invoiced by the miners. TEP expects to recover these costs over the remaining life of the mines, which is estimated to be between 14 and 20 years.

[6] TEP and UNS Electric will request recovery from FERC for the prudent costs incurred to develop a high-voltage transmission line from Tucson to Nogales. TEP and UNS Electric are not going to proceed with the project. See Note 7.

[7] Net Cost of Removal for Interim Retirements represents amounts recovered through depreciation rates associated with asset retirement costs expected to be incurred in the future.

[8] The Deferred Investment Tax Credit relates to federal energy credits generated in 2012 and is amortized over the tax life of the underlying asset.